This invention relates to a hydromechanical transmission, primarily for track-laying vehicles. It incorporates a series of planetary assemblies in conjunction with a hydrostatic driving module and also a hydrostatic steering module.
The invention relates to the problem of obtaining efficient operation of a track-laying vehicle. It may be considered to be an improvement of the invention shown in my U.S. Pat. No. 3,888,139, as particularly adapted to track-laying vehicles.
In one preferred form thereof it provides a four-stage transmission which may operate either in forward or in reverse in all four stages or ranges. It enables rapid change from forward to reverse to occur smoothly without the usual clutch changing delays and enables the very efficient operation of the track-laying vehicle both in moving straight forward on in straight reverse or in making turns. In the hydrostatic (starting) mode, the change from forward to reverse is made by changing the direction of slope of the swash plate of a hydraulic unit. In the hydromechanical mode or modes, forward or reverse operation is obtained by engagement of a forward clutch or a reverse clutch. All clutch engagements are synchronous including the initial engagement for startup.